Back-knife wood-turning lathe



K. F. WITT BACKKNIFE WOOD-TURNING LATHE June 7, 1960 5 Sheets-Sheet l Filed May 16, 1957 INVENTOR. KENNETH F.f wm.

ATT'Y.

June 7, 1960 K. F. WITT BACK-KNIFE woon-TURNING LATHE 5 Sheets-Sheet 2 Filed May 16, 1957 INVENTOR.

KENNETH E WITT.

June 7, 1960 K. F. WITT BACK-KNIFE woon-TURNING LATHE 5 Sheets-Sheet 3 Filed May 16, 1957 INVENTUR.

. KENNETH F. WITT.

gamma-Mgg Jurze 7, 1960 Filed May 16, 1957 5 Sheets-Sheet 4 INVENTOR. KENNETH F. WITT.

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June 7, 1960 Filed May 16, 1957 K. F. WITT 2,939,496 BACK-KNIFE {Noon-TURNING LATHE v 5 Sheets-Sheet 5 INVENTOR.

KENNETH E WITT.

@Kw-GF United States Patent BACK-'KNIFE WOOD-TURNING LATHE Kenneth F. Witt, Winchendon, Mass., assiguor to Goodspeed Machine Company, Winchendon, Mass., a corporation of Massachusetts Filed May 1-6, 1957, ser. No. 659,690.

1 claim. (ci. 142-17) Vvertically-movable back-knife. i f

It is theV general objeictof-A my invention to provide improved. operating mechanism for a lback-knife Woodturning lathe, to the intent that more rapid and reliable operation may be attained: I also provide improved control mechanism by which a desired sequence of operations may be automatically performed.

My invention further relates to arrangements and combinations of parts which will be hereinafter described and more particularly pointed out in the appended claims.

A preferred form of the invention is shown in the drawings, in which Fig. 1 is a front elevation of aback-knife lathe embodying my improvements but with certain parts omitted; Fig. 2 is `a plan view of the lathe, looking in the direction of the arrow 2 in Fig. 1;

" Fig. 3V is la diagrammatic view, partly in section,

showing the operative relation of certain parts, together with certain control circuits therefor; s

Fig. 3a is a detail sectional view of a clamping device to be described; Y

Fig. 4 is la diagram showing the control circuits in relation to the separate mechanisms controlled thereby;

Fig. 5 is a partial side elevation, partly in section, showing control and operating mechanism for a movable tool carriage;

Fig. 6 is a plan view of certain valve mechanism, taken substantially along the :line 6 6 in Fig. 5;

Figs. 7, 8 and 9 are sectional elevations, taken along the lines 7-7, 8-'8 and 9 9 in Fig. 6; 1

Fig. 10 is a longitudinal sectional v-iew of certain valve mechanism associated with the headstock clamping means; and

Fig. L1 is a longitudinal sectionalview of certain valve mechanism and an operating cylinder for the back-knife elevating apparatus.

Referring to Figs. 1 and 3, my improved lathe comprises a fra-me F supporting a movable headstock H and a xed but axially `adjustable tailstock T. A piece of lwork W is mounted between a work-driving center. 10 in the headstock Hand a tail center 12 in the tailstock T. The driving spindle 10a is connected by a plurality of belts 14 to 4any suitable driving mechanism, not shown. The driving center 10 has a centering spur and transversely-disposed driving edges of the usual type.

Patented June 7, 1960 2 ated with the frame 22 and extend upward from the frame 22 and are engaged by gears 27 on a cross shaft 28 having a pulley 2.9 which is connected by a chain or belt 30 to a counterbalancing air cylinder 31.

' Air under pressure in the cylinder 31 is allowed to escape gradually during the downward movement of the back-knife and is built up during upward movement of the knife, as shown in detail in Fig. 1l.

The cylinder 31 (Fig. 1l) has a piston 310- having a piston rod 311 directly connected by the chain 30 to the pulley 29 (Fig. 3). A control valve 312 has an inlet connection 313 from an air pressure supply, also an exhaust outlet 314 and a connection 315 tothe cylinder v Loading mechanism Special provision is made for automatically inserting fresh pieces of work, as W', vbetween the drive center 10 andthe tail center 12.` Y j For this purpose, segmental arms 35 (Fig. 3) are mounted on a longitudinally extending shaft 36 rotatably supported in iixed bearings at the back of the machine. The free or swinging ends of the arms 35 support a frame or holder 37 adapted to receive the workpiece W and in which the fresh workpiece is to be inserted manually.

The shaft 36 has an Iarm 37 actuated by anoperating cylinder 38. The upper part of the cylinder 38 is connected to the lower part of a dash-pot 38a. The upper part of the dash-pot is connected by a pipe 40 to an air-supply and control valve mechanism S2 to be further described.V When oil is forced into thel cylinder 38 by the supeiposed air pressure, Va'piston rod 39 (Fig. 3) is drawn upward and the arms 35 are swung forward to present the workpiece W' between the centers 10 and 12. During such movement, the workpiece W is held from displacement by a pivoted holding arm 41 which is moved to engage the workpiece by admission of air through a branch pipe 40a to a cylinder 42. The holding arm 41 is thus caused to operate in timed relation to the positioning arms 35. The activation of the loading mechanism by lthe solenoid-operated valve 52 is controlled by a switch D, as will be later described.

The tail center 12 is freely rotatable on suitable antifriction bearings.

The usual back-knife 20 is mounted for longitudinal angular adjustment in a supporting frame 22, which is vertically'slidable in fixed guideways 23 and 24. Y Vertically slidable rack bars A25 and 26 (Fig. 3) are associ- Driving spindle operation YThe mechanism for axially shifting the driving spindle 10 and for applying driving pressure thereto is best shown in Fig. 3. Y.

A cylinder 44 is Vmounted in a normally xed base 44a, and a piston 45 in the cylinder is connected by a piston rod 46 to the slidable headstock H supporting the `drivingspindle 10a. The cylinder 44 is connected by a pipe 50 and solenoid-operated valve mechanism S3 to a compressed-air supply pipe 52. The other end of the vcylinder 44 is similarly connected by a pipe 54 to the valve mechanism S3 and by a by-pass 54a' to a valve mechanism S5 (Figs. 3 and V10). A

When air under pressure is admitted through the pipes 54 to the left-hand end of the xed cylinder 44, the headstock H and the driving spindle 10a will be advanced to force the workpiece W against the tail center 12 and 4to hold the work in driving engagement. When air is .flater admitted through .the rire 5l! tcthecylinder 44,

Y Y 3' the driving spindle will be withdrawn or moved to the left. A small chamber 56 extends upward from the pipe 54a and is normally closed by a spring-pressed cap or valvemember 57 (Fig. 10). -Whenair pressure builds up in the cylinder 44 after the driving center was engaged the work, the valve member 57 will be lifted andair under pressure will pass through the port 58 (Fig. l0) to a cylinder 59 and will move a relatively large piston 60 to eject oil from the opposite end of a cylinder 59a through a port 59b and a pipe 61 to a pressure tube 62 laterally engaging the headstock H. The tube 62 is preferably of the rectangular construction shown in Fig. 3a, with the right-hand end closed and with the left-hand end connected to the pipe 61.

When pressure is applied to the tube 62, the tube is pressed lirmly against the side llange 44b of the headstock H. The headstock H is thereby held firmly in its adjusted axial position. The control and operation of the solenoid valve S3 will be hereinafter described.

Roughng tool carriage operation The tool carriage 34 (Figs. 2 and 3) is slidably mounted on the frame F and carries a tool 65 which removes the corners from the square block or workpiece W and also carries a roughing tool 66 which is pivotally mounted on the carriage 34 and which is shiftable in a vertical plane by engagement of a control arm 67 (Fig. 2) with a roughing templet 68 (Fig. 2) mounted in the lower central portion of the Ilathe. The function of the tool 66 and templet 68 is to reduce the workpiece to dimensions which roughly approximate the desired finished contour. The actual and desired finished contour is then provided by the operation of the back-knife in its continued downward movement.

A supporting ring 70V (Fig. 3) encircles the workpiece directly behind the cornering knife 65 land takes the lateral thrust of the roughing knife 66 as the work is turned. A supply of oil or grease is injected through the'ring 70 from a grease cup 71 to which air under pressure is supplied through a small pipe 72. The lubricating means is separately claimed.

Tool carriage feeding mechanism The mechanism for feeding the tool carriage 34 is shown in detail in Figs. 3 and 5 to 9. A cylinder 80 houses a piston 81 which is connected by a piston rod 82 to the tool carriage 34 and preferably at a medial point thereof. The cylinder 80 is operated by oil under pressure supplied from a tank 84 (Fig. 3). Y

The tank 84 contains a partition 84a which partially separates the oil in the lower portion of the tank from `an air space 85 in the upper portion of the tank. Air is supplied from a pressure pipe 87 (Fig. 3) through a solenoid-operated valve S1 and a connecting pipe .88. A number of upright partial partitions 85b lin the upper space 85 slowdown the lair-llow from the pipe 88.

The lower portion of the tank 84 which contains the oil is connected by a pipe 90 to a valve cylinder 91 in the valve mechanism S4, and this cylinder is connected by a pipe 92 and a hand-set valve 93 to a passage 94 opening into the cylinder 80 and providing operating pressure for the piston 81 to move the carriage 34 at regulated speed to the left in Fig. 3. The gooseneck intake 90a for the pipe 90 facilitates smoothvoperation.;

The solenoid-operated air-intake valve S1 also has an air connection 96 to the left-hand end of the cylinder 80. When this connection is open and under pressure, air is admitted to the cylinder 80 to move the piston 81 to ,the right at increased speed, and at the same time to force the operating oil back through the described'connections to the lower part of the tank 84. The rapid return movement of the piston 81 builds up oil pressure :ahead of the piston 81 and forces the spring-pressed plug 4 94a to the right in Fig. 3, thus opening a direct oil return through pipes 95 and 90 back to the tank 84.

A branch by-pass 94b introduces oil to increase the pressure on the plug 94a, through the by-fpass 95a (Fig. 3). It is sometimes desirable to reduce the rate of travel of the cutting tools, and such action is achieved through the operation of the solenoid-operated valve S4, best shown in Fig. S. An air pipe 96a is connected into a fitting 97 which has a cross passage 98 connecting to the left-hand end of the valve cylinder 91.

The connection from the pipe 96a to the passage 98 is commonly closed by a spring-pressed solenoid plunger 100. When this plunger 100 is moved to the left in Fig. 5 by its solenoid 100a (Fig. 5), the pipe 96a is opened through the passage 98 to the left end of the valve cylinder 91.

The piston 101 (Fig. 5) will then be moved to the right against the Vpressure of the spring 102 to close the connection from the pipe 92 and to provide a by-pass connection through a pipe 105 Iand a hand-set needle valve 106 by which the flow of oil to the cylinder 80 may be reduced to any desired amount.

General operation The general operation of the machine can be best described by reference to the diagram shown in Fig. 4. This diagram ydiscloses a series of switches A, B, C, D and E, solenoid-operated valves S1, S2, S3, S4 and pressure-operated valve mechanism S5, relaysY Rand R2 and a series of manually opel-able circuit closures N and N2 to N6.

The approximate locations of the contact switches A to E are shown in Fig. 3, where the switch A in the upper center of the igure is positioned to be closed by an adjustable stud associated with the shaft 36 which operates the work feed.

The switch B is shown atthe left of the workpiece W', and is actuated by engagement with a shoulder on the Vtool`carriage 34 as it approaches its 'left-hand limit of travel.

The switch C is below the left-hand end of the carriage feed cylinder 80 and is engaged by the tool carriage 34 as it reaches its right-hand or return limit of travel.

The switch D is shown above the headstock H and is engaged by a lug 122 movable with the headstock H.

The switch E is shown at the left of the lower portion of the tank 84 and is engaged by an adjustable plate 124 which is movable vertically with the back-knifeV frame 22.

The operational sequence of the machine is as follows:

The machine is inoperative so long as the starting switch N remains open after a working cycle has been completed. The tool carriage 34 is then in its right-hand or return position, and in this position it will have closed the switch C. 1 If the switch N is then manually closed, current will pass through the switch C from the line wire L and through a solenoid-operated valve S2 to the return line wire L.

The solenoid in S2 will raise the valve piston to the 'position shown in Fig. 4, so thateoil under air pressure will be admitted to open the work-clamping member 41 and then swing the loading arms 35V forward.

Completion of the loading motion causes the lug 120 Ato close the switch A, thus activating the solenoid in a relay R. This relay in turn activates the solenoid-operated valves S1 and S3.

The valve piston in S3 is then raised to admit air Vthrough the pipe 54 to the fixed headstock cylinder 44, thus quickly advancing the driving spindle 10a and center l0 against the operatively positioned workpiece and forcing the work against the tail center 12.

Y AtV the same time, the valve piston in the solenoid S1 75 Vis raised to admit air tothe upper part of the tank 84.

This air builds up -oil pressure in the tank 84 and starts the forward travel of the tool carriage 34.

The interchange of air and oil pressure in the tank 84 produces a limited delaying action, so that the driving spindle comes into operation before the carriage 34 is advanced to cutting position.

As the head center 10 reaches driving position, the lug 122 on the headstock H opens the switch D, thus breaking the circuit through the solenoid-operated valve S2, releasing the work-holding arm 41, and allowing the centering arms 35 to swing back to initial position.

When the desired travel of the tool carriage 34 to the left is completed, the carriage engages and closes the switch B which thereupon activates the solenoid in the relay R2. The closing of this relay activates the lower solenoid coil in the valve units S1 and S3, and thus reverses the air circuits and causes return movements of the driving spindle 10 and the carriage 34.

It will be noted that the 4oil in the tool carriage cylinder 80 is -forced rapidly back to the tank 84 by the application of air pressure to the left-hand side of the piston 81 and by opening the lby-pass 95.

Return of the head spindle allows lthe switch D to close, and at the end of the return travel of the carriage 34, Athe switch C is engaged and closes, thus initiating a new cycle of operation. Y

The switch E is engaged bythe plate 124 `at any desired point in the travel of the carriage 34, and when so engaged, it shifts the flow of oil to the carriage feed cylinder 80 from the relatively open passage through the pipe 92 to the relatively restricted passage through the pipe l activate any selected pant of the machine for setting or testing.

Having thus described my invention and the advantages thereof, I do not wish to be limited tcthe details herein disclosed, otherwise than as set forth in the claim, but what I claim is: p

In a wood-turning lathe having a back-knife and mechanical operating means electivei to lower and raise said back-knife, that improvement which comprises auxiliary air-operated counterbalancing apparatus having a mechanical `operating device connected to said mechanical operating means, and said mechanical operating device being effective to apply a lifting force to said backknife, and said `auxiliary air-operated counter-balancing apparatus including an air-pressure valve device which has a by-pass admission passage and an auxiliary exhaust passage, and said valve device having an air cylinder, a control piston movable in one direction in said air cylinder to admit air under pressure from an air supply passage to said mechanical operating device and movable in the opposite direction to connect said mechanical operating device to the atmosphere, and means in said air cylinder which is eiective to move said control piston to open said exhaust passage and to close said air-supply passage when the air-pressure in said by-pass admission passage is substantially relieved.

References Cited in the le of this patent UNITED` STATES PATENTS 583,375 Hood May 25, 1897 1,733,208 Schimmel Oct. 29, 1929 1,804,720 Turcott May 12, 193i1 1,912,184 Ferris et al. May 30, 1933 2,012,493 Barnes Aug. 27, 1935 2,294,138 Strock Aug. 25, 1942 2,370,322 Nebesar Feb. 27, 1945 2,422,357 LeTourneau June 17, 1947 2,570,660 Gamble Oct. 9, y1951 2,713,283 Lomazzo July 19, 1955 2,739,717 Dinsmore Mar. 27, 1956 

